It is generally known to provide individual optical elements on or in one or more surfaces of optically transmissive substrates including films, sheets or plates for redirecting light passing through such substrates. These optical elements may be three-dimensional optical elements of well defined shape each having a length and width substantially smaller than the length and width of the substrates rather than continuous optical elements that run substantially the full width or length of the substrates.
When a larger pattern of these individual optical elements is desired, one known fabrication method is to tile together multiple first or second generation copies of a master having the desired pattern of individual optical element shapes thereon to produce a larger pattern of the individual optical element shapes that is used to make the larger pattern of optical elements on or in the substrates. This substantially cuts down on the machining time that would be required to make a master having the larger pattern of individual optical element shapes therein.
In the case of non-overlapping optical element shapes or optical element shapes that overlap in a regular pattern, it is relatively easy to align the edges of copies of the master during tiling of the copies together so that minimal disruptions in the pattern of optical element shapes is evident in the larger pattern. However, when the overlapping optical element shapes in the master are substantially random, the edges of the copies that are made from the master will normally align in a fashion that causes substantial discontinuities in the optical element shapes along the edges and hence the pattern at large. Thus there is a need to be able to minimize any discontinuities in a larger pattern of substantially random optical element shapes where the edges of the copies meet.